Nowadays, digital compass (called electronic compass as well) made of magnetoresistive material is popular in the navigation, location and vectoring field, which aims at measuring the geomagnetic field direction. Comparing with the conventional compass, the digital compass possesses the prominent advantages including small size, low consumption, low cost, high sensitivity, high frequency response and the like.
As the resistance of the magnetoresistive material varies with the external magnetic field, thus the digital compass can achieve the magnetic field measurement by utilizing this effect. Generally, the digital compass made of magnetoresistive material uses a two-axis or three-axis geomagnetic sensor to measure the geomagnetic field components on the X-axis, Y-axis (and Z-axis) respectively, and a two-axis or three-axis acceleration sensor for measuring the pitching angle and the roll angle. And the geomagnetic azimuth angle can be measured out according to the above data information.
FIG. 1 shows a conventional digital compass 500 includes a two-axis geomagnetic sensor 501 for detecting the geomagnetic azimuth angle, an acceleration sensor 502 for detecting the titled geomagnetic angle on the basis of the horizontal line, an analog processor 503 for amplifying and filtering the signal detected by the geomagnetic sensor 501 and the acceleration sensor 502, an analog/digital converter 504 for converting the output signal into digital signal, and a digital processor 505 for calculating a geomagnetic azimuth angle on the basis of the digital signal received from the analog/digital converter 504, and performing the calibration process. Concretely, the geomagnetic sensor 501 is adapted for measuring the magnetic field intensity of the earth, which includes an X-axis sensor and Y-axis sensor arranged in right angle. The acceleration sensor 502 measures the pitching angle and the roll angle for compensating the titled coordinate.
However, the output signal and the measurement accuracy are the main issue always. As mentioned, the above digital compass must receive the digital signal to perform calibration process. Additionally, the output signal of the geomagnetic sensor 501 may change and vary with the outer environment suddenly, which causes the offset of the output signal of the digital compass to vary with the outer environment abruptly. Thus, the measurement accuracy of the geomagnetic azimuth angle is decreased. Furthermore, the above digital compass with complex structure causes a high cost as well.
Thus, there is a need for an improved digital compass with an improved geomagnetic sensor device to overcome the above drawbacks.